/* =======================================================================
   Mutex example: deadlock because not unlocking a mutex...
   ======================================================================= */

#include <iostream.h>
#include <stdlib.h>
#include <pthread.h>

int N;				// Shared variable
pthread_mutex_t N_mutex;	// Mutex controlling access to N

pthread_t tid[100];

void *worker(void *arg)
{
   int i;


   for (i = 0; i < 10000; i = i + 1)
   {
      pthread_mutex_lock(&N_mutex);
      N = N + 1;  
//    pthread_mutex_unlock(&N_mutex);   -- See what happens now...
   }

   cout << "Added 10000 to N" << endl;

   return(NULL);     /* Thread exits (dies) */
}

/* =======================
   MAIN
   ======================= */

int main(int argc, char *argv[])
{
   int i, num_threads;

   /* -----
      Check command line
      ----- */
   if ( argc != 2 )
   {
      cout << "Usage: " << argv[0] << " Num_Threads" << endl;
      exit(1);
   }


   /* -----
      Initialize mutex
      ----- */
   pthread_mutex_init(&N_mutex, NULL); 

   num_threads = atoi(argv[1]);

   N = 0;		// Do we need pthread_mutex_lock(&N_mutex); ???
			// ??????

   cout << "Setting N to 0" << endl;

   /* ------
      Create threads
      ------ */
   for (i = 0; i < num_threads; i = i + 1)
   {
      if ( pthread_create(&tid[i], NULL, worker, NULL) )
      {
	 cout << "Cannot create thread" << endl;
	 exit(1);
      }
   }

   for (i = 0; i < num_threads; i = i + 1)
      pthread_join(tid[i], NULL);

   cout << "N = " << N << endl << endl;

}